Architectural aluminum goes green

By Tammy Schroeder, LEED GAThe green building movement offers unprecedented opportunity to respond to challenges like global climate change, dependence on non-sustainable and expensive sources of energy, and threats to human health. The work of innovative building professionals is a fundamental driving force in the green building movement. Such leadership is a critical component to achieving the Canada Green Building Council’s (CaGBC’s) vision of a transformed built environment leading to a sustainable future.

The GREEN UP Program, launched by CaGBC in 2009, provides performance standards and resources to help building owners and operators understand and measure ongoing performance of the building envelope and to assist in finding efficiencies and improvements to achieve reductions in energy use, water use, and greenhouse gas (GHG) emissions.

By adopting green strategies within a building, not only are efficiencies and savings established, but employee productivity is also improved, and economic and environmental performances are maximized. Green building methods can be integrated at any stage—from design through construction to renovation and maintenance. The most significant benefits are obtained when the design/construction team takes an early, integrated approach evaluating the whole building system throughout its entire lifecycle.

Considering not just the whole building, but multiple buildings’ impact on their communities, the “2011 U.S. and Canada Green City Index”—commissioned by the electronics/electrical engineering manufacturing company, Siemens Corp.—found Vancouver to be the second greenest city in North America, closely following San Francisco. Toronto ranked ninth. Survey indicators ranged from water and energy consumption and conservation to public use of land, public transportation quality and efficiency, and even a city’s ‘walkability.’

Canada’s cities also are increasing the number of buildings registered and certified with the Leadership in Energy and Environmental Design (LEED) rating system. Last year, CaGBC reported 861 registered LEED buildings in 2010, with 143 certified. This is up significantly from 2009 numbers of 551 registered and 57 certified. Office buildings made up 35 per cent (or 303) of the projects registered or certified in 2010.

Building-integrated photovoltaic (BIPV) systems featuring aluminum frames may be finished in paint or anodize, or a dual finish. With the latter, paint may be used on the exterior and anodize on the interior, or vice versa. Different colour schemes also may be specified to match the architectural palettes.Photo courtesy Wal-Mart Stores Inc.

Such green projects earn their certification by including overt, visible technologies like renewable energy systems, high-performance HVAC assemblies, or reused building materials. However, there are also more ‘subtle’ aspects to sustainable design, including the finishes for aluminum components. While coatings and paints can offer the right esthetic impact and improved durability, they also provide potential for other ‘hidden’ benefits, including improved daylighting and energy efficiency.

Paints and coatings from a green perspective
Daylight harvesting has the most significant effect on LEED in the category of Energy and Atmosphere (EA) credits. Natural light can reach the building interior through windows and skylights, or by reflecting off interior or exterior surfaces.

Multiple studies have proven ample access to daylight and a pleasant view out of a window supports better outcomes in employee productivity, faster patient recovery, and higher performance in student learning. Daylight varies throughout the day, leading to piqued visual interest. The eyes adapt easily to this gradual illumination change, which is not easily achievable with artificial light.

Research has suggested a positive biological response to daylight’s variability. A properly-designed office that incorporates daylighting measures can provide a bright or soft mood created by the intrinsic colour, the intensity of the light source, and the use of warm interior colours. Working by daylight is reported to result in less stress and discomfort leading to better occupant comfort and health.

Use of windows and skylights have also demonstrated a positive and significant correlation to higher sales in retail stores. A cross-sectional field study by the Heschong Mahone Group (HMG) statistically demonstrated that, all other things being equal, an average non-skylit retail store would be likely to have 40 per cent higher sales with the addition of daylighting devices.

Beyond the personal and profitable benefits of sunlight, natural lighting also can contribute to optimizing energy use within a building. When seeking energy savings, one must look first to reduce the energy demand. Selecting daylight material, coated in a high solar reflective index (SRI) system—such as infrared (IR) reflective fluoropolymer coatings—can have an impact. High solar reflectance (i.e. albedo) and high-emittance coatings play an important role in resisting heat absorption and keeping buildings cooler, which reduces energy needed for air-conditioning systems.

In March 2011, a major coatings manufacturer issued a white paper that showed when IR reflectance coatings increased from five to 70 per cent for metal wall, window frame, and the roof, then the total building energy costs were reduced by one per cent in cold-weather cities such as Ottawa, Boston, and Chicago. (The reduction was up to four per cent in warm-weather cities such as Mexico City and Phoenix.) (“Energy Savings in High-rise Buildings Using High-reflective Coatings,” commissioned by a manufacturer, can be found online).

The Canadian/U.S. border patrol station in Niagara Falls features an aluminum curtain wall with sunshades and a custom trellis. Finished in a 70 per cent PVDF two-coat liquid paint product, the aluminum framing withstands the challenging environmental conditions of temperature fluctuations, excess moisture from the river and falls, and exhaust from traffic. A dual-coloured finished presents visitors from each country with a different scheme: bright silver for the Canadians and dark green for the Americans.Photos courtesy Wausau

Whether baking in the sun or freezing in the cold, building envelopes endure some of the most rigorous daily durability challenges. Selecting an exterior architectural finish that will have the longest lifespan possible can be a daunting task. Since LEED’s introduction in 1998, the ‘green explosion’ has increased awareness of the various finishing options and their performance criteria. The finishing technologies and processes involved in design, construction, and manufacturing are extremely important to a building’s longevity and sustainability.

In the architectural and commercial industry, the three types of factory-applied, high-performance finishes for aluminum are:

polyvinylidene fluoride (PVDF) paint;

powder coat; and

anodize.

Each process can be applied securely and permanently to the building’s aluminum components, with environmental protection inherent in the finish.

The finish choice is usually based on a combination of personal taste and performance specifications. Selecting the appropriate finish for the building’s exterior involves much more than just choosing a colour. Conversing with an applicator that has experience with all three finish types can be beneficial in determining the best application.

Unless applied onsite, architectural finishes do not contribute to the attainment of the LEED Indoor Environmental Quality (EQ) Credit 4.2, Low-emitting Materials–Paints and Coatings, but they most assuredly do contribute to a building’s sustainability.

Sustainable considerations of PVDF paint
High-performance 70 per cent PVDF coatings allow selection of nearly any conceivable colour (or combination), while shielding the building against aging, weathering, and pollution. PVDF coatings have been a proven mainstay in the architectural market since their introduction in 1965.

The resin system incorporated into the paint determines the coating’s characteristics and performance properties. The carbon-fluorine bond used in PVDF resin-based coating is one of the strongest bonds known.

The primary environmental concern with liquid paints is the solvents used to deliver the paint to the part. Some of these solvents are considered volatile organic compounds (VOCs)—when released directly into the atmosphere, they contribute to ozone depletion. However, environmentally conscious finishers employ a 100 per cent air capture system and destroy the VOCs with a regenerative thermal oxidizer to eliminate this impact. VOC content is off-gassed and cured at the factory before arrival at the building site. Construction damage repair and restoration of architectural projects originally finished in a 70 per cent PVDF coating can be refinished onsite by professional applicators using the same type of high-performance coating in an air-dry system.

In Canada and the United States, liquid PVDF coatings have long been specified for curtain walls, windows, skylights, doors, building panels, and other architectural components. In recent years, manufacturers have also made great strides in developing high-performance architectural powder coatings, with some companies manufacturing these products with the same resin system used in liquid PVDF coatings.

Some North American powder coat companies promote the use of their product in the European market; for decades, powder coating has been the preferred coating method for aluminum across the Atlantic. However, European architectural powder coatings are made from a chemistry that does not meet AAMA 2605 requirements. A recent study noted the highest European standard, Qualicoat, is similar in quality only to AAMA 2604—an intermediate specification that utilizes 50 per cent PVDF coatings. The highest Qualicoat standard requires less exposure to the elements and calls for routine washing of all exterior metal building components—an expensive proposition for building owners. One should be cautious when selecting a powder coat finish to validate it meets the AAMA 2605 specification.

Demonstrating the durability of liquid PVDF coatings, the Canadian/U.S. border patrol station in Niagara Falls (shown on page 30) features an aluminum curtain wall system with sun shades and a custom trellis finished in a 70 per cent two-coat product. Manufactured in the mid-1990s, the curtain wall withstands the challenging environmental conditions of temperature fluctuations, excess moisture from the river and falls, and exhaust from traffic. While the station provides an enduring, unified structure, visitors from each country are greeted by a different colour scheme: the aluminum framing for the U.S. elevation is coated in dark green, while the Canadian one is finished in bright silver.

Sustainable considerations of anodize
In the 1920s, aluminum turned the ‘metals world’ upside down with its benefits of light weight, strength, fabrication flexibility, and durability. The first finishing technology developed was the anodize process, which provided corrosion-resistant, long-lasting protection and colour on the aluminum surface. Most building owners and architects call for architectural anodize for its beauty, but long life and low maintenance are also important factors.

Please check the box below to confirm you would like to be added to Kenilworth Media’s various e-mail communications (includes e-newsletters, a survey now and then, and offers regarding the design-build industry*).

Leave this empty:

YES, I CONSENT

*We do not sell your e-mail address to 3rd parties, we simply forward their offers to you. Of course, you always have the right to unsubscribe from any communications you receive from us, should you change your mind in the future.

Please check the box below to confirm you would like to be added to Kenilworth Media’s various e-mail communications (includes e-newsletters, a survey now and then, and offers to the design-build industry*).

YES, I CONSENT

*We do not sell your e-mail address to 3rd parties, we simply forward their offers to you. Of course, you always have the right to unsubscribe from any communications you receive from us, should you change your mind in the future.